1. Field of the Invention
This invention relates to a printing apparatus, such as a printer and a copier, and to a printing method, and more specifically to a printing apparatus and a printing method that can control vibration generated resulting from movement of a carriage capable of carrying a printing head to be small. Especially, the invention relates to a printing apparatus and a printing method that, when the printing apparatus is installed on an installation base, such as a table and a rack, can control vibration of the installation base and other devices installed on the installation base to be small.
2. Description of the Related Art
Conventionally copiers and printers are well known as the printing apparatus. As for the printer, for example, there is one that has a movable carriage carrying a printing head and uses a serial scanning method. Carriages in the printers of this method each make a reciprocating movement in a direction (main scanning direction) that intersects a conveyance direction (in a sub scanning direction) of a printing medium, such as paper and film (hereinafter referred to also as “printing sheet,” “paper,” and “paper form”). The printing head does printing scanning while moving with the carriage. By repeating such printing scanning and a conveyance operation of a printing medium, an image is printed on the printing medium. The printer of such a serial scanning method has spread widely for reasons that the structure can be simplified and the like.
The carriage is made to make a reciprocating movement accompanying a printing operation by using, for example, a driving source of a DC motor etc. and driving force transferring means of an endless timing belt etc. Generally, the carriage goes to an acceleration state in which the moving speed increases gradually after starting of the movement in one direction, and changes to a constant speed state. In this constant speed state, the printing head prints an image on the printing medium. After completion of such printing scanning in the one direction, the carriage is controlled to go to a deceleration state in which the moving speed decreases gradually and stop at a predetermined position. Subsequently, after conveying a predetermined amount of paper form, the carriage is made to start the movement in the other direction and controlled in driving as in the printing scanning in the one direction, whereby the printing head performs printing scanning in the other direction.
Generally, the printing apparatus including such a printer is used being put on the installation base, such as a table, rack, or the like. At that same time, on this installation base, there is often the case where a personal computer (also called a PC) for transmitting desired print information and creating and processing the desired printing information and a monitor device for displaying various pieces of information that this personal computer handles are installed. Moreover, in the so-called rack etc., generally, the whole system is configured in such a way that a printing apparatus is installed at a position higher than the personal computer, the monitor device, etc.
When installing the printing apparatus in such a table, rack, or the like and making it operate, the table, rack, or the like is likely to vibrate caused by reactive force generated by a driving source, such as a motor, for driving the carriage inside the printing apparatus and translation of a center-of-gravity position of the printing apparatus resulting from movement of the carriage itself. Moreover, there is a possibility that installed objects, such as a personal computer, on this table, rack, or the like are caused to vibrate. For example, when installing the printing apparatus on a table, rack, or the like, and making it operate, there is a possibility that a natural vibration period of a whole system including the installation base, such as a table and a rack, and installed devices, such as the printing apparatus and the personal computer, becomes resonant with a period of the reciprocating movement of the carriage.
FIG. 11 is a diagram illustrating a case where a table, rack, or the like fall in a resonant state. FIG. 11 shows temporal variation of the acceleration in a carriage scanning direction during the printing operation and temporal variation of the acceleration of the neighborhood of the printing apparatus in a rack on which the printing apparatus is installed in the carriage scanning direction. FIG. 11 clearly shows that the movement of the carriage causes a vibration of the rack close to a sinusoidal wave, resulting in an almost resonant state of the carriage and the rack. When the carriage and the rack become in such a condition, the table or the rack or the like will vibrate greatly.
As a method of preventing such large vibration, a vibration prevention base equipped with a function of attenuating the vibration of a printing apparatus, such as a printer, that is a generation source of vibration is known. Such vibration prevention bases have various configurations. For example, there are one that is equipped with a damper using elasticity or viscosity etc., one that controls vibration by absorbing horizontal vibration generated by a printer using a rack and pinion on an arc (e.g., see Japanese Patent Application Laid-open No. 4-141480 (1992)), and the like.
Moreover, a method is proposed where a vibration sensor for detecting vibration of a table, rack, or the like is provided in a printing apparatus, a plurality of parameters each consisting of a speed at which a carriage is moved and a stop time at the time of reversing a movement direction of the carriage are prepared in advance, and the carriage is driven based on one set of parameters (e.g., see Japanese Patent Application Laid-open No. 2000-071539). In this method, in advance of the printing operation, the carriage is made to make a reciprocating movement based on predetermined parameters from among the plurality of parameters and a swing detection sensor detects swing of the installation base at this time. Then, if the swing of the installation base exceeds a predetermined value, another parameter is selected from among the plurality of parameters and the carriage is made to make a reciprocating movement based on the newly selected parameter, and the swing of the installation base is detected. The parameter with which the swing of the installation base becomes equal to or smaller than (hereinafter described as “not larger than” for simplicity) the predetermined value is selected, and the parameter with which the swing of the installation base becomes not larger than the predetermined value is used fixedly to drive the carriage.
However, in the case where vibration of the installation base and the installed devices installed on the installation base that is generated resulting from operations of the printing apparatus is prevented by the conventional configuration and a method like this, the following new problems will arise. That is, in order to equip an installation base of a printing apparatus etc. with a vibration prevention function, it is necessary for a user to newly purchase an installation base equipped with the vibration prevention function in addition to a table, rack, or the like on which the printing apparatus is installed, which makes it difficult to use such printing apparatus cheaply.
Moreover, in a configuration as disclosed in Japanese Patent Application Laid-open No. 2000-071539, a plurality of carriage speeds and a plurality of stop times at the time of starting the reciprocal movement are used; a carriage speed and a stop time that minimize the vibration of the printing apparatus are selected and subsequently the speed and the stop time thus selected are used fixedly. Therefore, when desiring a printing result such that movements of the carriage differ widely, round-trip times of the carriage are made different in various ways, and consequently it is likely that an effect of preventing the vibration of the printing apparatus cannot be achieved sufficiently.
Furthermore, in order to fully achieve the vibration prevention effect in the printing apparatus, it is necessary to fix the selected speed of the carriage and the selected stop time at the time of reversing a movement direction. As a result, the movement of the carriage (scanning width) will be fixed, and accordingly the one round-trip time of the carriage will be fixed. Therefore, even when the movement of the carriage required for actual printing (scanning width) is small compared to the movement of the carriage determined for the selected speed, it is necessary to make the carriage move for the movement as determined previously for the selected speed. As a result, a time required for printing will become long.